MATLAB: Several Operations Within a Matrix Matlab

columncomparingmatrixrepitition

i'd like someone with knowledge on matlab to help me sort this out, the plan is to write a script as follow
it starts reading numbers on column 2 and check in column 3 one if they are repeated: The Condition is, if a number in column 2 is repeated more than one time in column 3, the corresponding values in column 4 will be summed up, if a number from column 2 is not repeated or only repeated one time in column 3, its corresponding value in column 4 will be left as it is. The obtained values would be generated in a vector. the letters were put there just for explanation here is an example to try with
data=[0   1    0     0
      1   2    1    200
      2   3    1    300
      3   4    1    400
      4   5    2    500
      5   6    3    600
      6   7    4    700
      7   8    5    800
      8   9    5    900
      9   10   5    1000
      10  11   6    1100
      11  12   7    1200
      12  13   7    1300];
this would be the desired result
v=[(200+300+400) 200 300 400 (800+900+1000)  600 (1200+1300)  800 900 1000 1100 1200 1300]
waiting on any ideas.Thank you programmers !

Best Answer

data=[0   1    0     0
      1   2    1    200
      2   3    1    300
      3   4    1    400
      4   5    2    500
      5   6    3    600
      6   7    4    700
      7   8    5    800
      8   9    5    900
      9   10   5    1000
      10  11   6    1100
      11  12   7    1200
      12  13   7    1300];
D = diff(data(2:end,3),1);
E = [false;~D] | [~D;false];
tmp = cumsum(diff([false;E])>0);
out = data(:,4);
idx = data([false;diff([false;E])>0],3);
out(idx) = accumarray(tmp(E),data([false;E],4));
And this code's output compared to your example output:
>> [out,v]
ans =
         900         900
         200         200
         300         300
         400         400
        2700        2700
         600         600
        2500        2500
         800         800
         900         900
        1000        1000
        1100        1100
        1200        1200
        1300        1300
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